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Inertia Tensor and Center of Gravity Measurement for Engines and Other Automotive Components
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 2, 2019 by SAE International in United States
This content contains downloadable datasetsAnnotation ability available
A machine has been developed to measure the complete inertia matrix; mass, center of gravity (CG) location, and all moments and products of inertia. Among other things these quantities are useful in studying engine vibrations, calculation of the torque roll axis, and in the placement of engine mounts. While the machine was developed primarily for engines it can be used for other objects of similar size and weight, and even smaller objects such as tires and wheels/rims.
A key feature of the device is that the object, once placed on the test table, is never reoriented during the test cycle. This reduces the testing time to an hour or less, with the setup time being a few minutes to a few hours depending on the complexity of the shape of the object. Other inertia test methods can require up to five reorientations, separate CG measurement, and up to several days for a complete test.
The device uses a system of pivots, springs, and three sensors to get the three moments and three products of inertia, plus the CG location. Object mass is measured separately on a scale. A stable pendulum arrangement is used to get the CG location, two moments and one product of inertia. A rotating plate with springs is used to get one moment of inertia, and a load cell is used to get two products of inertia. For typical passenger-vehicle engine-size objects accuracy is on the order of 2.5 mm for CG, 1% for moments of inertia, and 2% of the smallest moment for products of inertia.
The three sensors used are an inclinometer, a load cell, and a rotary encoder. Custom software is used to record the measurements from the sensors. The software performs all calculations, guides the user through the test sequence, and checks for possible testing errors.
CitationAndreatta, D., Heydinger, G., Zagorski, S., and Guenther, D., "Inertia Tensor and Center of Gravity Measurement for Engines and Other Automotive Components," SAE Technical Paper 2019-01-0701, 2019, https://doi.org/10.4271/2019-01-0701.
Data Sets - Support Documents
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- Heydinger, G.J., Durisek, N.J., Coovert, D.A., Guenther, D.A. et al., “The Design of a Vehicle Inertia Measurement Facility,” SAE Technical Paper 950309, 1995, doi:10.4271/950309; Also presented and reprinted by invitation at the 1995 Society of Allied Weight Engineers (SAWE) International Conference, May 1995.
- Andreatta, D.A., Heydinger, G.J., Bixel, R.A., and Coovert, D.A., “Inertia Measurements of Large Military Vehicles,” SAE Technical Paper 2001-01-0792, March 2001, doi:10.4271/2001-01-0792; Also presented and reprinted at the 2001 Society of Allied Weight Engineers (SAWE) International Conference, 2001.
- Durisek, N.J., Heydinger, G.J., Chrstos, J.P., and Guenther, D.A., “Land Vehicle Roll/Yaw Product of Inertia Measurement, Transaction of the ASME,” ASME Journal of Dynamic Systems, Measurement and Control 119:212-216, June 1997.
- Durisek, N.J., Heydinger, G.J., Chrstos, J.P., and Guenther, D.A., “Non-Rigid Body Product of Inertia Measurement: Application to Land Vehicle Dynamics,” ASME “Transportation Systems- 1994” DSC-Vol. 54, November 1994, 375-386.
- Chrstos, J.P., Heydinger, G.J., and Guenther, D.A., “Error Analysis Techniques Applied to Vehicle Inertial Parameter Measurement, ASME Transportation Systems- 1992,” DSC 44:97-112, December 1992.
- Durisek, N.J. and Heydinger, G.J., “Calibration Fixture Design for Vehicle Center of Gravity Height and Inertia Measurements, Vehicle Research and Test Center (VRTC) Final Report,” DTNH22-94-P-08424, April 1995.
- McGarry, Joshua E., “Small Parts Inertia Tester,” Thesis for M.S. degree in Mechanical Engineering, The Ohio State University, Columbus, OH, March 2004.
- McGarry, J.E., Andreatta, D.A., Heydinger, G.J., and Guenther, D.A., SAWE Paper No. 3340, Category No. 6, 2004 Society of Allied Weight Engineers (SAWE) International Conference, May 2004.
- Weight Engineer’s Handbook, Revised Ed., Society of Allied Weight Engineers, Los Angeles, CA, May 2002, 5.18.